7:40 is a great time for a reservation to try to catch Illuminations at 9:00! You can ask for a table outside w/ a view, but they usually can't/won't let you wait for one. Particularly if it's busy, you usually have to just take the next available table. They'll let you over to their viewing section, though, if you're seated somewhere w/out a view when the show starts.
(My first response showed up before your question. Glitch??)